1. Field of the Invention
The present invention relates to a method of and an apparatus for measuring a three-dimensional shape, and more particularly to a method of and an apparatus for measuring a three-dimensional shape by causing a three-dimensional measuring unit mounted on a robot to trace the surface of a workpiece to measure the surface shape of the workpiece.
2. Description of the Related
Three-dimensional measuring units can measure the position and shape of a workpiece by tracing the surface of the workpiece. Heretofore, it has been customary either for the person who is to measure the workpiece to carry a three-dimensional measuring unit and trace the surface of the workpiece with the three-dimensional measuring unit, or to install a three-dimensional measuring unit on a dedicated gatepost-shaped coordinate measuring device for measurement. If the person directly holds the three-dimensional measuring unit for measurement, then it is burdensome for the person when it takes a long time to measure the workpiece. Further, the gatepost-shaped coordinate measuring device is of a complex structure and is expensive.
In view of the above, efforts have recently been made to install a three-dimensional measuring unit on the arm of a robot and to operate the three-dimensional measuring unit to measure the surface shape of a workpiece.
There has been proposed a similar technology for recognizing reference points set in an external space or a workpiece with a position measuring unit and measuring the shape of a recognized measurement area with a laser scanner (see, e.g., Japanese Laid-Open Patent Publication No. 2003-505682 (WO01/007866)).
If a robot is used to measure the surface shape of a workpiece, then it is necessary to train the robot for measuring operation, and to establish reference teach points. Though it is a simple task to establish teach points, it takes a significant amount of time because the number of teach points involved is large. Particularly, when workpieces to be measured are provided in various types, it is necessary for the operator to retrain the robot for each workpiece type, and hence is burdensome for the operator.